/*
 * This file may have been modified by Bytedance Ltd. and/or its affiliates (“ Bytedance's Modifications”).
 * All Bytedance's Modifications are Copyright (2023) Bytedance Ltd. and/or its affiliates.
 */

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once

#include <string>
#include <assert.h>
#include <stddef.h>
#include <string.h>

namespace DB
{
class Slice
{
public:
    // Create an empty slice.
    Slice() : data_(""), size_(0) { }

    // Create a slice that refers to d[0,n-1].
    Slice(const char * d, size_t n) : data_(d), size_(n) { }

    // Create a slice that refers to the contents of "s"
    Slice(const std::string & s) : data_(s.data()), size_(s.size()) { }

    // Create a slice that refers to s[0,strlen(s)-1]
    Slice(const char * s) : data_(s), size_(strlen(s)) { }

    // Intentionally copyable.
    Slice(const Slice &) = default;
    Slice & operator=(const Slice &) = default;

    // Return a pointer to the beginning of the referenced data
    const char * data() const { return data_; }

    // Return the length (in bytes) of the referenced data
    size_t size() const { return size_; }

    // Return true iff the length of the referenced data is zero
    bool empty() const { return size_ == 0; }

    // Return the ith byte in the referenced data.
    // REQUIRES: n < size()
    char operator[](size_t n) const
    {
        assert(n < size());
        return data_[n];
    }

    // Change this slice to refer to an empty array
    void clear()
    {
        data_ = "";
        size_ = 0;
    }

    // Drop the first "n" bytes from this slice.
    void remove_prefix(size_t n)
    {
        assert(n <= size());
        data_ += n;
        size_ -= n;
    }

    // Return a string that contains the copy of the referenced data.
    std::string ToString() const { return std::string(data_, size_); }

    // Three-way comparison.  Returns value:
    //   <  0 iff "*this" <  "b",
    //   == 0 iff "*this" == "b",
    //   >  0 iff "*this" >  "b"
    int compare(const Slice & b) const;

    // Return true iff "x" is a prefix of "*this"
    bool starts_with(const Slice & x) const { return ((size_ >= x.size_) && (memcmp(data_, x.data_, x.size_) == 0)); }

private:
    const char * data_;
    size_t size_;
};

inline bool operator==(const Slice & x, const Slice & y)
{
    return ((x.size() == y.size()) && (memcmp(x.data(), y.data(), x.size()) == 0));
}

inline bool operator!=(const Slice & x, const Slice & y)
{
    return !(x == y);
}

inline int Slice::compare(const Slice & b) const
{
    const size_t min_len = (size_ < b.size_) ? size_ : b.size_;
    int r = memcmp(data_, b.data_, min_len);
    if (r == 0)
    {
        if (size_ < b.size_)
            r = -1;
        else if (size_ > b.size_)
            r = +1;
    }
    return r;
}

}
